Packaging machine

ABSTRACT

The present invention relates to a packaging machine having at least one working station which has a lower and/or an upper tool, being vertically movable on lifting tables and the lifting table having  
     a vertically displaceable plate onto which the lower tool is mounted,  
     at least one vertical guide for said plate,  
     a crankshaft,  
     a bar, one end of which being connected rotatably about at least one axis to the plate and the other end rotatably to the crankshaft, and  
     a rotatable drive driving the crankshaft.

[0001] The present invention relates to a packaging machine having atleast one working station which has a lower and/or an upper tool, thelower tool being vertically movable on lifting tables.

[0002] Such packaging machines are well-known from the prior art.

[0003] Thus, for example, EP 0,569,937 B1 discloses a packaging machinehaving a working station which includes a lifting device wherein thelower tool is lifted or lowered by a toggle lever system and a pistoncylinder means. However, such a lifting device requires an enormousamount of space, thereby unnecessarily increasing the length of thepackaging machine. Moreover, the lifting mechanism is relatively slowand complex because e.g. two toggle levers are required to avoid tiltingof the plate at the guide bars.

[0004] It was therefore the object to provide a packaging machine thatwould not involve the drawbacks of prior art.

[0005] According to the invention, said object is accomplished by meansof a packaging machine having at least one working station which has alower and/or an upper tool, the lower tool being vertically movable onlifting tables and the lifting table having

[0006] a vertically displaceable plate onto which the lower tool ismounted,

[0007] at least one vertical guide for said plate,

[0008] a crankshaft,

[0009] a bar, one end of which being connected rotatably about at leastone axis to the plate and the other end rotatably to the crankshaft, and

[0010] a rotatable drive driving the crankshaft.

[0011] A working station in the meaning of the invention is e.g. a deepdrawing, a sealing and a cutting station.

[0012] In a preferred embodiment, the bar is arranged in the center ofthe plate. This embodiment is advantageous in that the plate neverundergoes tilting.

[0013] In another preferred embodiment, the crankshaft runs rotatably onbearings in two yokes. The yokes themselves are adjoined to the frame ofthe packaging machine. Preferably, the yokes are arranged transverselyto the machine direction of the foil so that the length of theconstruction of each working station is designed to be particularlyshort.

[0014] Bearing the crankshaft on two yokes is advantageous in that theimmense forces occurring during lifting and pressing the plate with thelower tool against the upper tool can very well be passed into thevertical guide without bending and/or tilting the crankshaft.

[0015] Preferably, the vertical guide of the plate consists of a bar,more preferably of two bars, with four bars being particularlypreferred. The plate itself has at least one, preferably two guidebushings receiving the bars.

[0016] In a preferred embodiment, the yokes run on bearings preferablyat the bottom end of the bars, and preferably in a verticallydisplaceable fashion, each one yoke being held by two bars. Thisembodiment of the packaging machine according to the invention isadvantageous in that each working station represents an entity which canbe displaced as a whole within the packaging machine, or demounted.

[0017] Advantageously, each bar has a spring element, preferably anelastomeric spring attached thereto, where the vertically displaceableyokes rest on. This embodiment of the packaging machine according to theinvention is advantageous in that foils of varying thickness or withrelatively large tolerances with respect to their thickness can beprocessed without necessitating changes in the lift adjustment. Anincreased foil thickness then results in a minimal increase in force.Moreover, the press-on pressure of the lower tool against the upper toolcan be limited by said springs.

[0018] The crankshaft preferably is driven by an electric motor,preferably a servomotor which preferably is computer-controlled. Theelectric motor preferably has a gear, the power transmission between theelectric motor or gear and the crankshaft preferably being effected by atoothed belt. The electric motor or gear preferably has such a hightorque and such a high rotational speed that the plate together with thelower tool is lifted within less than one second, preferably within lessthan one half second from the bottom to the top position and vice versa.

[0019] Moreover, the electric motor or the gear at the power take-offside preferably has a retention momentum of >50 Nm, more preferably >100Nm, so as to be capable of absorbing the forces occurring e.g. duringsealing or cutting where the bar connecting the plate with thecrankshaft is not in vertical position.

[0020] Preferably, the crankshaft is rotated alternately in a clockwiseand counterclockwise fashion. Surprisingly, such an arrangement wasfound to be highly space-saving. The angle of rotation is 180° atmaximum. However, the crankshaft preferably moves by an angle ofrotation having precisely such a magnitude that the tool will not damagethe package trough as it moves further on. In a particularly preferredfashion, the tool is lowered by such a distance that its top edge is1-10 mm below the package trough at maximum. As a result of suchlowering, a substantial reduction of the cycle time of the packagingmachine according to the invention is possible.

[0021] The packaging machine of the invention is advantageous in thatthe vertical movement of the lower tool is carried out within less thanone second. Production and maintenance of the lifting table are easy.Because the bar contacts the plate at the center thereof, tilting of theplate at the guide is excluded.

[0022] A preferred embodiment of the packaging machine according to theinvention includes a means for avoiding product squeeze between upperand lower tools. Preferably, such a means involves limiting theadmissible consumption of power required for the upward motion of thelower component. Is there any product between upper and lower tools, itwill be compressed between the upper and the lower tool, therebyincreasing the consumption of power required to lift the lower tool, andthe motor control will stop the upward motion.

[0023] With reference to FIGS. 1-3, the invention will be illustratedbelow. These illustrations are merely by way of example and do not limitthe general idea of the invention.

[0024]FIG. 1 shows a schematic side view of a packaging machine withlateral cover omitted;

[0025]FIG. 2 shows a side view (in machine direction of foil) of thelifting table;

[0026]FIG. 3 shows a side view (across the machine direction of foil) ofthe lifting table.

[0027]FIG. 1 shows the packaging machine of the invention in schematicview. A foil 1 is unrolled from a roll, initially passing through a deepdrawing station 2 comprised of an upper tool 3 and a lower tool 4. Thelower tool 4 is mounted on a plate 5 which, as indicated by the arrow,can be lifted and lowered. In the deep drawing station 2, the foil 1 isdeformed to yield a package trough 6.

[0028] Thereafter, the package troughs 6 are filled with an item to bepackaged, and the package troughs are sealed with a cover foil in thesubsequent sealing station 10. Similarly, the sealing station 10 iscomprised of an upper tool 12 and a lower tool 11, and the lower tool 11can be lifted and lowered in the sealing station as well.

[0029] Finally, the packages are cut apart in cutting station 7. Again,the cutting station is comprised of an upper tool 8 and a lower tool 9,and the lower tool 9 can be lifted and lowered in the cutting station aswell.

[0030] The lifting table, by means of which the lower tools 4, 9, 11 arelowered and lifted, is illustrated in FIGS. 2 and 3, each one permittinga different view on the lifting table. FIG. 2 shows the lifting table inlowered condition, while the lifting table in FIG. 3 has been lifted.

[0031] The lifting table has a plate 13, onto which the lower tool 4, 9,11 is mounted. The plate is provided with two guide bushings 14receiving the guide bars 15. On its bottom side, the plate 13 has abearing 16, wherein the top end 18 of bar 17 is accommodated pivotablyabout one axis. At its bottom end 19, the bar 17 is rotatably connectedwith crankshaft 20 which, in turn, runs on bearings in yokes 21, 22. Theyokes 21, 22 run on bearings on bars 15 in a vertically displaceablefashion, resting on elastomeric spring 26. This type of bearing allowsautomatic adjusting of the lift to the thickness of the foil. At thesame time, it is made sure that the press-on pressure by means of whichthe lower tool is pressed against the upper tool does not exceed aspecific maximum value. In addition, such a bearing of the yokes allowsexcellent adjustment of the press-on force. The lower tool and thelifting device thereof can be displaced as an entity within thepackaging machine, or demounted. The crankshaft 20 is driven by theelectric motor 24 via toothed belt 23. The motor is controlled in a wayso as to alternately rotate the crank of the crankshaft from the highestto the lowest point and vice versa, said rotation being effectedalternately in a clockwise and counterclockwise fashion. The spacing 25is dimensioned in a way so as to correspond to at least half the depthof the deepest processable package trough on the respective packagingmachine. The electric motor 24 has a gear. The electric motor or gear isdimensioned in such a way that one rotation of the crankshaft isperformed in less than one second. In addition, the electric motor 24has a retention momentum of >10 Nm, so that the gear at the powertake-off side has a retention momentum of >100 Nm in order to allowabsorption of forces occurring during the respective processingoperation, particularly in cases where the bar 17 is not in absolutelyvertical position.

1. A packaging machine, having at least one working station (2, 7, 10)which has a lower and/or an upper tool (3, 8, 12), the lower tools (4,9, 11) being vertically movable on lifting tables, characterized in thatthe lifting table has a vertically displaceable plate (13) onto whichthe lower tool (4, 9, 11) is mounted, at least one vertical guide (15)for said plate (13), a crankshaft (20), a bar (17), one end (18) ofwhich being connected rotatably about at least one axis to the plate(13) and the other end (19) rotatably to the crankshaft (20), and arotatable drive driving the crankshaft.
 2. The packaging machineaccording to claim 1, characterized in that the bar (17) is arranged inthe center of plate (13).
 3. The packaging machine according to claim 1or 2, characterized in that the crankshaft on its right and left runs onbearings in yokes (21, 22).
 4. The packaging machine according to any ofclaims 1 to 3, characterized in that the vertical guide (15) iscomprised of a bar, preferably of two bars, with four bars beingparticularly preferred.
 5. The packaging machine according to claim 4,characterized in that each one yoke (21, 22) runs on bearings on twobars (15) in a vertically displaceable fashion.
 6. The packaging machineaccording to claim 5, characterized in that each yoke rests on twospring elements (26).
 7. The packaging machine according to claim 6,characterized in that one spring element (26) is mounted to one bar (15)each time.
 8. The packaging machine according to claim 6 or 7,characterized in that the spring elements (26) are elastomeric springs.9. The packaging machine according to any of claims 1 to 8,characterized in that driving is performed using an electric motor,preferably a servomotor, and preferably via a toothed belt.
 10. Thepackaging machine according to claim 9, characterized in that the motorhas a retention momentum of >10 Nm.
 11. The packaging machine accordingto claim 9 or 10, characterized in that the motor can be rotated in twodirections.
 12. The packaging machine according to claim 11,characterized in that the crankshaft is rotated alternately in aclockwise and counterclockwise fashion by 180° at maximum.
 13. Thepackaging machine according to claim 12, characterized in that the angleof rotation of the crankshaft is adjusted in such a way that the tool(4, 9, 11) is lowered by only such a level that the package trough isnot damaged as it moves further on.
 14. The packaging machine accordingto claim 13, characterized in that the top edge of the tool (4, 9, 11)during lowering is lowered by only 1-10 mm below the bottom edge of thepackage trough.
 15. The packaging machine according to any of claims 1to 14, characterized in that the lifting time is 1 second at maximum,preferably 0.5 seconds at maximum.
 16. The packaging machine accordingto any of claims 1 to 12 and 15, characterized in that the spacing (25)corresponds to at least half the depth of the package trough (6). 17.The packaging machine according to any of claims 1 to 16, characterizedin that the packaging machine includes a means to avoid squeezing ofproducts between upper and lower tools.
 18. The packaging machineaccording to claim 17, characterized in that the means comprises alimitation of the admissible consumption of power during the upwardmotion of the lower tool.